Backpack



FIG. 1 is a front left perspective view of a backpack, showing the new design;

FIG. 2 is a front right perspective view thereof;

FIG. 3 is a front elevational view thereof;

FIG. 4 is a rear elevational view thereof;

FIG. 5 is a left-side elevational view thereof;

FIG. 6 is a right-side elevational view thereof;

FIG. 7 is a top plan view thereof; and,

FIG. 8 is a bottom plan view thereof.

The broken lines showing stitching form no part of the claimed design. 

CLAIM I claim the ornamental design for a backpack, as shown and described. 